While polymeric materials have replaced or reduced the use of traditional metal-based materials, the general lack of strength and wear resistance have impaired more widespread use. Even in engineering applications where the use of polymeric materials such as polyurethane provide a cost advantage, improved wear resistance would greatly improve the durability of equipment currently made from polymeric materials. In addition, improved wear resistance would expand their use into other applications.
It is to be understood that the following reference to prior art should not be taken as evidence that the references form part of the common general knowledge.
In the prior art, there are numerous examples of inorganic materials such as abrasives being added to polymers. Pat. No JP 05250666 discloses dispersing an abrasive separately to form a slurry and adding the slurry to a paint composition to obtain magnetic paint. Solvents for the dispersion of the abrasives preferably include ethers, esters, aromatic hydrocarbons, aliphatic hydrocarbons and chlorinated hydrocarbons. Binder resins for the dispersion are preferably modified vinyl chloride, polyurethane and polyester resins. Abrasives preferably include alumina, aluminum silicates, silicon carbide, chromium oxide, nitride, titanium oxide and boron oxide. The abrasive: resin ratio on dispersion is preferably 4:8. The method improves dispersability of magnetic powders and abrasives achieve high filling density and high smoothness of the surface of the medium.
Pat. No. WO 98/51736 relates to a method of producing a rigid polyurethane and/or polyisocyanurate foams by reacting a polyol with a polyisocyanurate, and adding an inorganic solid finely dispersed in a liquid phase in quantities ranging from 0.01 to 9 weight percent. The preferred inorganic additive includes SiO2, TiO2, Fe2O3, CdS, CdSe, tungsten carbide, silicon, silicon carbide and ferric sulfide.
U.S. Pat. No. 6,190,770 B1 describes pulsed voltage surge resistant enamelled wires that outlines a shield coating layer containing a synthetic resin, an organic solvent and α-form Al2O3 particles and γ-form Al2O3 particles. The synthetic resins can be polyacetal, polyurethane, polyester, polyesterimide, polyesterimine, polyimine, polyamideimide, polyamide, polysulfone, polyimide resins or mixtures thereof. The organic solvent used depends on the chosen resin and can be cresols, hydrocarbons, dimethyl phenol, toluene, xylene, ethylbenzene, N,N-dimethyl formamide (DMF), N-methyl-pyrrolidone (NMP), esters, ketones or mixtures thereof. The Al2O3 particles are added within a range of 3-20 wt %, with a particle size range of 0.001-10 μm, and are uniformly dispersed by high shear mixing. Optionally, a dispersant can be used to facilitate dispersion. The preferred resin are polyamideimide or polyesterimide and the solvents are a mixture of xylene, NMP and DMF or xylene, hydrocarbons, cresols and phenols, and preferred particle size for Al2O3 particles are 0.3-0.5 μm, at a loading of 5-10%.
However, thermoset polymeric precursors by their nature are relatively viscous prior to curing at lower temperatures and generally not able to sustain higher temperatures. Therefore mixing particulate inorganic materials into a polymeric resin inevitably results in the inclusion of air bubbles which seriously affect the mechanical properties of any articles produced from the polymer composite mixture. In addition, settling of heavier inorganic particulates in lighter polymer fluid results in poor dispersion and inhomogeneous properties.
It is an object of the present invention to provide a method of preparing a polymer inorganic particle composite which has improved wear resistant properties without reducing the strength properties of the polymer.